With recent developments in optical communication technology, optical switches have been sought that allow high-speed response, size reduction, high integration, low power consumption, and reduction of signal attenuation.
Conventionally-known optical switches include the ones in which liquid crystal is used, optical fibers are moved by a mechanical device using an electromagnet, a micromirror is used and so forth.
However, the optical switch using liquid crystal performs switching on the basis of molecular orientation, so that the optical switch has been slow in response and has not been easily adapted to optical communication requiring high-speed communication. There also has been a problem in that utilization efficiency of light is low since a polarizing plate has to be employed.
In the optical switch in which optical fibers are moved by a mechanical device using an electromagnet, the device could not be reduced in size and it has been difficult to meet the demands for a high degree of integration. Additionally, there has been a problem in that power consumption is large as switching is performed by the mechanical operations of an electromagnet.
In the optical switch using a micromirror, the manufacturing process becomes complex and the manufacturing costs are thus high, which is troublesome. There also has been a problem in that attenuation of signals is large since the light is required to propagate through the atmosphere.
In addition to these optical switches, an optical switch is proposed that performs switching by utilizing the change in refractive indexes of optical waveguides due to electro-optic effects during the application of electric fields to the optical waveguides.
However, in this type of optical switch, there is a problem in that the switch is likely to be affected by interference from electric fields applied by other switches by which the other optical waveguides are controlled. Particularly, when an optical switch is reduced in size, electrodes to apply electric fields to each optical waveguide inevitably get close to each other, increasing the interfering effect of electric fields between adjacent optical waveguides and generating errors due to crosstalk and so forth, which has been troublesome.
Additionally, an optical switching element has been proposed that has: a light guide portion for performing light transmission by confining light internally by total reflection; an optical switching portion for extracting the light confined internally to the outside of the light guide portion when the optical switching portion is in contact with the light guide portion, and then reflecting the extracted light into the direction of the desired light guide portion; and a driving portion for driving the optical switching portion (JP-A-11-202222).
However, this optical switching element is configured to let the light guide portion extend light transmission of input light only in one direction. At the same time, the switching element unintentionally outputs the light that is input to the light guide portion, to the outside by contacting the switching portion to an unspecific total reflecting plane of the light guide portion. In other words, the switch only turns light on or off. Accordingly, the following configurations cannot be achieved: a switching element as an optical switch that outputs specific input light after switching or dividing the optical path thereof to a plurality of specific output side ends; an optical switch that outputs a plurality of specific input light to specific output ends by switching each optical path of the input light; and a multichannel optical switch that outputs a plurality of specific input light after switching or dividing the input light to a specific plurality of output ends. Although the switching element may be applicable to objects such as an image display, it has been practically difficult to apply the switching element to an optical communication system.
Moreover, in addition to the configuration whereby the light guide portion extends light transmission only in one direction, the optical switching element is configured to utilize infinitely repeated total reflection of the light guide portion. Thus, an emitting direction at the switching portion, in consideration of refraction at an interface between atmosphere and the light guide portion, is restricted to a deeper angle than the total reflection angle thereof; in other words, an almost vertical direction to the total reflecting plane. Even in this sense, switching to transmit light into different directions for each specific light could not be performed.